At a command prompt, type diskpart.
At the DISKPART prompt, type select disk 0. ( umjesto nule stavi broj diska kojeg zelis ocistiti)
At the DISKPART prompt, type clean all.
At the DISKPART prompt, type exit.
Makar mislim da tebe muci EFI a ne bootloader od windowsa, prouci si ovo
https://www.rodsbooks.com/refind/